1. Field of the Invention
The present invention relates to the general art of manufacturing, and to the particular field of an I.D. collet for chucking against an internal opening of a workpiece to hold that workpiece in position for machining, such as a lathe, milling or grinding.
2. Brief Description of the Prior Art
In manufacturing various types of workpieces having large openings there through, it frequently becomes necessary to chuck or grasp the workpiece internally. For example, in machining or grinding a tube or cylinder, it frequently is necessary to hold the cylinder internally rather than externally.
Conventional internal diameter chuck devices, commonly referred to as I.D. collet chucks, are made of a tube having a longitudinally slotted wall, with the internal opening in the tube being tapered. A drawbar inserted in the tube, and having a wedge-shaped outer surface, spreads the tube for grasping or chucking against the wall defining the opening in the workpiece.
Other conventional I.D. collet chucks are essentially as described above but with ramifications of the internal shape of the slotted collet tube, such as using a double taper, that is, tapering from both ends of the tube and using a double tapered drawbar arrangement.
While these prior devices have been in use for many years, they have significant drawbacks. In particular, the following problems have been noted by the inventor. If while using the prior art devices in a production environment and a part spins and scours the outside surface of the spindle or if it is an automatic machine and it misloads and activates the draw bar, then the pull shaft will keep pulling the taper screw back until it blows the locating diameter way over-size. Since the material of these prior devices is generally made of low carbon steel, they will not return to their original size. Accordingly, the workman or operator is now faced with making a new spindle and having a very expensive machine standing idle while the new I.D. collet chuck is being made. This generally results in a significant waste of time and expense.
There is therefore a need in the art to provide an improved I.D. collet which prevents the aforementioned damage to the present day I.D. collet devices.
There is a further need in the art to provide an improved I.D. collet which easily allows a spindle to be replaced with another spindle.